Digilent 6003-410-000P-KIT - Manual (Page 40)

40 www.xilinx.com XUP Virtex-II Pro Development System
UG069 (v1.0) March 8, 2005
Chapter 2: Using the System R
• Independently adjustable input volume controls with mute and a maximum gain of
12 dB and attenuation of 34.5 dB in 1.5 dB steps
• 3D stereo enhancement
•
PC Beep tone input passthrough to Line Out
The TPA6111A audio power amplifier supports the following features:
•
Fixed Gain
•
Stereo Power Amplifier delivers 150 mW per channel into 16
Ω
•
Click and Pop suppression
The National Semiconductor LM4550 uses 18-bit Sigma-Delta A/Ds and D/As, providing
90 dB of dynamic range. The implementation on this board, shown in
Figure 2-12 , allows
for full-duplex stereo A/D and D/A with one stereo input and two mono inputs, each of
which has separate gain, attenuation, and mute control. The mono inputs are a
microphone input with 2.2V bias and a beep tone input from the FPGA. The
BEEP_TONE_IN (TTL level) is applied to both outputs, even if the CODEC is held in reset
to allow test tones to be heard. The CODEC has two stereo line-level outputs with
independent volume controls. One of the line-level outputs drives the audio output
connector and the second line-level output drives the on-board power amplifier shown in
Figure 2-13 .
The power amplifier is capable of producing 150 mW of continuous power per channel
into 16
Ω loads, such as headphones. The assertion of the AUDIO_AMP_SHUTDOWN
signal by the CODEC causes the audio power amplifier to turn off.
The TPA6111A audio power amplifier contains circuitry to minimize turn-on transients,
that is, click or pops. Turn-on refers to either power supply turn-on or the device coming out
of CODEC controlled shutdown. When the device is turning on, the amplifiers are
internally muted until the bypass pin has reached half the supply voltage. The turn-on
time is controlled by C9.
The power amplifier was included to support two output modes, line out mode and power
amp output mode. The line level output attenuation is controlled by the CODEC volume
control register 04h, and the power amp output attenuation is controlled by CODEC
volume control register 02h.